The Mobile communication network has evolved to the third generation (3G), and there are worldwide large-scale deployments of 3G networks and industry applications thereof. With the continuous population and promotion of data services and the Mobile Internet, the International Organization for Standardization is developing mobile communication LTE and the fourth generation (4G) and other technical standards, to meet the increasing development of network technology and service capacity. Because the MIMO (Multiple Input Multiple Output) technology may sufficiently take advantage of separate spatial transmission paths to greatly increase network service speed and link performance, it has become one of the cores of LTE and future 4G technology. The MIMO technology seeks to improve network service quality through deploying and establishing a plurality of antennas and adopting MIMO signal processing techniques. Generally, a LTE system requires a configuration of at least 2×2 MIMO or even more, for example, a TDD (Time Division Duplexing) LTE system generally requires 8 antennas to ensure the operational performance of MIMO.
With regard to 8 FDD (Frequency Division Duplex) antennas, in the MIMO mode, it is necessary to make the half power beamwidth of beams radiated from downlink transmission antennas of the 8 antennas be 65-degree. However, as shown in FIG. 1, various linear arrays in an array antenna are arranged side by side and severe cross-couplings will appear between any two linear arrays because of the very narrow space therebetween, therefore, it is highly possible that the beamwidth of the beam radiated from a downlink of each linear array will exceed 65 degrees, or even up to 80-90 degrees, which will result in that the constraint that the beamwidth of the beam should be 65-degree cannot be satisfied.